A cripple stud is a supportive construction element usually used above a door or above or beneath a window. They aren’t very different from other studs except that they are cut shorter to make room for the opening. The making of a cripple stud greatly depends on the size of the object that will be put around it.
Step 1 - Measure Opening
Measure the length of the window or door. Add four inches to this to compensating for the 2x4s placed around the window frame.
Determine how high up your window will rest and figure out how high the bottom cripple stud must be.
Step 2 - Calculate Stud Length
Add the length of the bottom cripple studs, the window and its frame and subtract it from the height of the wall. This will tell you how long the cripple stud will have to be above the window.
Step 3 - Cut Frame
Cut out these 2x4s and nail them to your frame. Around the window frame there will be a set of two boards that surround the entire frame.
Using a Cripple Stud above a Door
Building a door is essentially like building a window except that the cripple stud will be placed above the door and not below it.